1. Field of the Invention
The present invention relates to a plant supervisory system for supervising a process of a plant such as a nuclear power plant.
2. Description of the Related Art
In a conventional plant supervisory system, as shown in FIG. 22, when a plurality of computers 41 distributively processing functions, the computers 41 are connected with a shared memory unit 42 so as to share and exchange data thereamong.
Since process data is input from a control unit 43 of the plant to the computers 41 that distributively perform calculating processes, the process data is written to the shared memory unit 42 in such a manner that the computers 41 can reference the process data stored in the shared memory unit 42. And since it is necessary to exchange data among the computers 41, this exchanging is performed through the shared memory unit 42.
Thus, in the conventional function distributed plant supervisory system, the computers 41 are connected with the shared memory unit 42. Thus, the number of the computers 41 connected with the shared memory unit 42 depends on the storage capacity thereof. In other words, the number of the computers 41 connected with the shared memory unit 42 is restricted. Thus, many computers 41 cannot be connected. To solve this problem, a constitution of which several computers 41 share functions has been used.
In a plant supervisory system, it is desired to use small computers that distribute a process because of simple system constitution and easy functional expandability corresponding to desired functions and hardware scale. From this point of view, as a means for connecting computers, a method using a network has been proposed.
When computers 41 are connected through a network 44 as shown in FIG. 23, the number of computers 41 that can be connected increases. In fact, the number of computers 41 that can be connected is not restricted. Thus, the above-described problem can be solved.
On the other hand, to supervise the current state of the plant, each computer 41 should always reference the latest plant data. As shown in FIG. 22, in the system of which the computers 41 are connected with the shared memory unit 42, while a large amount of data is being exchanged among the computers 41, process data received from the control unit 43 can be written to the shared memory unit 42. Thus, the update time of the process data does not affect a process performed by the computers 41.
However, when computers 41 are connected through a network, since data that is exchanged among the computers 41 disturbs transmission of process data that is input from the control unit 43. Thus, the latest process data cannot be supplied to each computer 41.
The amount of data exchanged among the computer 41 largely varies corresponding to an operation of the operator and a state change of the plant. Thus, the amount of data transmitted on the network 44 varies. When the amount of data transmitted on the network 44 increases and exceeds the data transmission capacity of the network 44, the control unit 43 cannot transmit process data to each computer 41. Alternatively, process data transmitted from the control unit 43 to each computer 41 delays. Thus, it is very difficult to shorten the update time of the process data to a predetermined value or less.
As described above, in a plant supervisory system, because of simple system constitution and easy functional expandability corresponding to desired functions and hardware scale, it was desired to distribute a process with small computers. However, in the conventional system of which computers are connected with a shared memory unit, the number of computers connected with the shared memory unit is restricted. In other words, many computers cannot be connected.
To solve such a problem, a method for connecting much more computers through a network has been proposed. However, in this method, plant data may delay corresponding to the amount of data transmitted on the network. Thus, each computer cannot reference and process the latest plant data.
In addition, when small computers are connected through a network and a process is distributed thereamong, there are problems (1) to (5) that follow.
In such a plant supervisory system, a computer that processes each function is referred to as functional server. Examples of functional servers are a supervising server, a data collecting server, a performance calculating server, a plant operation assisting server, and an information managing server. The supervising server inputs process data, determines whether or not a process value is proper, and outputs the determined result. The data collecting server collects process data and stores the operation history of the plant. The performance calculating server performs a plant performance evaluating calculation corresponding to plant data. The plant operation assisting server outputs operation and guide information for an automatic plant operation and guide information for a plant unit operation test. The information managing server stores data received from each server. A computer that inputs process data and outputs the current value of the plant is referred to as a display control station. The display control station is an important unit that allows the operator of the plant to know the state of the plant.
(1) In the case that functional servers are redundantly constituted, if one functional server is broken down, data should be transferred to a backup functional server. However, the defective functional server cannot transfer data to the backup server. PA1 (2) In a nuclear power plant, TIP (Traversing Incore Probe) level should be periodically measured so as to obtain a real output distribution in the core of the reactor. The TIP level is normally measured by inserting a traversing incore probe into the core of the reactor. The TIP is traveled in the core. Position signals at around several hundred measurement positions are output. When the TIP position signals are output, TIP level signals are read. The TIP position signals are output from a TIP control unit at intervals of milliseconds. However, since the load applied to the CPU of a functional server fluctuates, it is difficult to collect the TIP level signals at high speed (on millisecond order). Thus, a data drop may take place. PA1 (3) When a function for comparing control rod sequences of the reactor is shared with another function by a server, the responsiveness of a control rod operation prohibition signal deteriorates. PA1 (4) Conventionally, a control command is output from a computer to the control unit through the network. When the responsiveness of which a computer directly controls the control unit is required, it is difficult to control the control unit through the network. PA1 (5) If an error takes place in the plant, a high speed data recording server collects information of a plant operation and analyzes the collected information. Thus, the high speed data recording server should collect process data at high speed without a data drop. Consequently, data that is buffered in time series by the process data input unit is transmitted. On the other hand, a functional server should use the current instantaneous value of the plant. Thus, conventionally, a first input unit that buffers process data and then transmits the buffered data and a second input unit that transmits an instantaneous value are used. The first input unit transmits data to the high speed recording server through its dedicated transmission path. The second input unit transmits data to a functional server through its dedicated transmission path. Thus, conventionally, two different process data input units are required.